Adaptations for spatial vision in sharks

The revelation that sharks as a group are not simply all‐rod, nocturnal vertebrates has called for a new perspective on their spatial visual capabilities. Using the lemon shark (Negaprion brevirostris) as a model species, selected components of spatial vision in sharks have been investigated. The physiological optics of the eye have been modeled with a schematic eye for the lemon shark, the first such model for an elasmobranch species. Retinal cone and ganglion cell topography and retinotectal projection pattern have been mapped completely for the first time in an elasmobranch. These topographic maps reveal a prominent visual streak, a functional specialization that is correlated with the lemon shark's visual behavior and habitat. Evidence in the literature of similar specializations for spatial vision in other elasmobranchs signifies that the lemon shark is not a special case. Assessments of the quality of shark vision should consider the sensory niches of these animals in their specific marine environments, as well as the phylogenetic and ontogenetic diversity within the group.